Seals, gaskets, O-rings,
enclosures and mastics can be highly sensitive to changes in pressure,
temperature and other conditions. Even worse is that many, while
forming a good barrier to water, allow water vapour to pass straight
through. Versaperm Limited, a world leader in water vapour permeability
measurement, has introduced a quick and simple way to test the materials,
the seals and the finished enclosures.

Water vapour is extraordinarily
invasive and the problems it causes have been estimated to cost
hundreds of millions of pounds in the UK each year. A simple programme
of testing is often all that is needed to ensure that seals are
effective – solving many of the problems that poor sealing
can cause.

The Versaperm WVTR (Water
Vapour Transmission) meter was designed for this task. It can cope
with several samples at a time, often give a reading in as little
as 30 minutes – whereas the conventional gravimetric measurement
technique takes several days and is significantly less accurate.

The WVTR meter is easy
to use and gives a series of digital readouts that can be recorded
or simply read off a screen. It needs no re-calibration and requires,
at most, minimal training to give results that are accurate to better
than one part per million (with some samples a few parts per hundred
million). Sensitivities are in the range 0.05 – 3200g/m2/day.

A wide range of variations is available, depending on the specific
application, but both single and multi-sample systems and a variety
of chambers are available for testing samples from the size of a
thimble up to a pallet load and beyond.

As well as manufacturing
the instruments, Versaperm also offers a water vapour permeability
laboratory service for companies that need to test samples on an
irregular basis.